Method and apparatus for performing a lateral flow assay

ABSTRACT

An embodiment of the present invention provides a method for performing a lateral flow assay. The method includes depositing a sample on a test strip at an application region, detecting a first detection signal arising from the test strip in the first detection zone, and generating a baseline for the first measurement zone by interpolating between values of the detection signal outside of the first measurement zone and inside of the first detection zone. The method may include locating a beginning boundary and an ending boundary for the first measurement zone on the test strip. Additional detection zones having measurement zones may also be incorporated with the embodiment.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention pertains to a method and apparatus forperforming and analyzing a lateral flow assay. More specifically, theinvention provides a method and apparatus for determining the amount ofan analyte present in a subject sample.

[0003] 2. Description of Related Art

[0004] Immunoassay technology provides simple and relatively quick meansfor determining the presence of analytes in a subject sample. Theinformation provided from immunoassay tests are often critical topatient care. Assays are typically performed to detect the presence ofparticular analytes, such as antibodies that are present when a humansubject has a particular disease or condition. Assays practiced underthe known art are numerous, and may include assays for diseases such asH. pylori, AIDS or conditions such as pregnancy.

[0005] The advancement of immunoassay technology now allows for assaytests to be performed without the complex and expensive equipment usedin hospitals and laboratory settings. Devices for performing assays arenow available for home or point of care use to quickly determine thepresence of a disease or condition. Such devices typically providequalitative results for the analyte or condition being tested for.Examples of such devices include strips that become visuallydistinguishable when the analyte being sought is detected.

[0006] However, devices for qualitative analysis of assays are oftenprone to user error, and lack the accuracy of sophisticated equipmentthat perform and analyze the assays in hospitals and laboratories. Forinstance, assay devices often require the user to visually interpret anongoing chemical reaction. In some applications, if the user mis-timesreading the assay device by even a few minutes, the result of the assaymay turn from negative to positive. Still, other devices fail tosufficiently distinguish positive from negative results.

[0007] Readers are provided in the known art for determining oranalyzing the results of assays more accurately. In general, readersprovide an improvement in that they may analyze an assay result, therebyremoving subjective factors that cause human error. However, whereasreaders may reduce operator subjectivity in reading or interpretingassay results, they do not help to control for or help mitigate othersources of assay variability. Such sources may include variabilityintroduced by incorrect assay run times, uncontrolled reactiontemperatures, or other possible operator-induced variability.

[0008] The present invention addresses these and other shortcomings ofthe known art.

SUMMARY OF THE INVENTION

[0009] It is therefore an object of the invention to provide a methodand apparatus for performing an assay in a variety of settings, such aspoint of care or near patient care and small laboratory settings.

[0010] It is another object of the invention to provide a method andapparatus that quantitatively analyzes results of a lateral flow assayto a high degree of accuracy.

[0011] Another object of the invention is to provide a method andapparatus for precisely controlling the timing of a lateral flow assayfor more accurate results.

[0012] Another object of the invention is to provide a method andapparatus for storing assay tables that may be selected to analyzemultiple lateral flow assays performed on a test strip.

[0013] Another object of the invention is to provide a method andapparatus to execute an algorithm that accurately analyzes the resultsof a lateral flow assay performed on a test strip.

[0014] And still another object of the invention is to provide a methodand apparatus to execute an algorithm that generates a baseline for thestrip to determine the results of a lateral flow assay.

[0015] With these objects in mind, an embodiment of the presentinvention provides a method for performing a lateral flow assay. Themethod includes depositing a sample on a test strip at an applicationregion, detecting a first detection signal arising from the test stripin the first detection zone, and generating a baseline for the firstmeasurement zone by interpolating between values of the detection signaloutside of the first measurement zone and inside of the first detectionzone. The method may include locating a beginning boundary and an endingboundary for the first measurement zone on the test strip. Additionaldetection zones having measurement zones may also be incorporated withthe embodiment.

[0016] In another embodiment of the present invention, a method forperforming a lateral flow assay includes providing a test strip on acartridge, where the test strip includes a first analyte binding agentcoupled to a detection agent and a second analyte binding agent. Themethod further includes depositing a sample on an application region ofthe test strip, where at least a portion of the sample binds to thefirst analyte binding agent coupled to the detection agent to form afirst analyte binding agent complex, the first analyte binding agentcomplex moving by lateral flow to a first detection zone that includes ameasurement zone, where at least a portion of the first analyte bindingagent complex binds to the second analyte binding agent in the firstmeasurement zone to form a second complex. In addition, the method alsoincludes detecting an intensity of a first detection signal arising inthe first detection zone, generating a baseline of signal intensity fromthe first measurement zone, and quantifying a value of signal intensityrepresentative of the second complex with respect to the baseline.

[0017] In another embodiment of the present invention, a method forperforming a lateral flow assay includes applying an electricalpotential across a pair of spaced apart electrical leads to create anelectrical field. The method further includes introducing a sample intothe electrical field to induce a change in the electrical field, thesample being spaced from the spaced apart electrical leads. The methodthen provides for initiating timing of the lateral flow assay upondetecting the change in the electrical field.

[0018] In another preferred embodiment, a method for performing alateral flow assay includes depositing a sample on a test strip of acartridge at an application region of the test strip, the test stripincluding a first detection zone with a first measurement zone. Themethod further includes inserting the cartridge in a housing having aprocessor and memory resources for storing a plurality of assay tables,selecting an assay table from a plurality of assay tables to perform thelateral flow assay on the test strip, detecting an intensity of adetection signal arising from a first detection zone of the test stripthat includes the first measurement zone, and quantifying a value ofsignal intensity for the first detection zone using a parameter from theassay table selected from the plurality of assay tables.

[0019] Another embodiment of the present invention provides an apparatusfor performing a lateral flow assay. The apparatus includes a housinghaving a receptacle for retaining a test strip that receives a sample.The apparatus also includes a sensor for detecting a first detectionsignal arising from a first measurement zone of the test strip. Aprocessor and memory resources generates the baseline for the firstmeasurement zone by interpolating between values of the detection signaloutside of the first measurement zone and inside of the first detectionzone.

[0020] Another embodiment of the present invention provides an apparatusfor performing a lateral flow assay that includes a pair of spaced apartelectrical leads contained within a receptacle of a housing. Theelectrical leads receive an electrical potential to create an electricalfield. A test strip is contained within the receptacle, the test stripbeing in sufficient proximity to the electrical leads to induce a changein the electrical field upon receiving a sample.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is an isometric view of a reader under the principles ofthis invention.

[0022]FIG. 2 is an isometric view of the cartridge having a test stripof a preferred embodiment.

[0023]FIG. 3 is a block diagram of a preferred embodiment of thisinvention.

[0024]FIG. 4 is a front view of the reader of a preferred embodiment.

[0025]FIG. 5 is a front isometric view of the reader of a preferredembodiment.

[0026]FIG. 6 is a block diagram of an autostart trigger preferred withthis invention.

[0027]FIG. 7 is a flow chart of an algorithm performed by a preferredembodiment for analyzing results of an assay.

[0028]FIG. 7A is a schematic of a model used by the algorithm of apreferred embodiment.

[0029]FIG. 8 is an illustrative data graph of the results attained bythis invention.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0030] This application hereby incorporates U.S. Patent Applicationentitled “Improved Lateral Flow Assays,” naming Alan Polito, RichardThayer, Robert DiNello, and George Sierra as inventors, filed Nov. 23,1998.

[0031] Now turning to the drawings, FIG. 1 shows a preferred embodimentof this invention to include a rapid assay reader 100 for performing andanalyzing lateral flow assays. The reader 100 includes a cartridgereceptacle 120 for receiving a cartridge having a test strip. A computersystem, such as a processor and memory resources, is contained withinthe reader 100 to control and analyze the assay. The computer system iscoupled to an input device such as a keyboard 130 and an output devicesuch as a display 140 to allow for user interaction in performing theassay. The reader 100 may include a battery and/or may be adapted tocouple to an AC power supply. A serial port or any other communicationoutlet may also be provided to upload or download software to and fromthe computer system contained within the reader 100. Steps included inperforming an assay under this invention include conducting the assay ona strip (shown in FIG. 2), and analyzing or interpreting the results ofthe assay conducted on the strip.

[0032]FIG. 2 shows in detail a cartridge 210 of a preferred embodiment,dimensioned to be received by the cartridge receptacle 120 (shown byFIG. 1). The cartridge 210 includes a front end 215 that inserts intothe cartridge receptacle 120, and a back end 290 that includes ahandling surface 280. A test strip 200 for performing a lateral flowassay is encased within the cartridge 210. Cartridge 210 may include asensor code for communicating with the computer system of the reader 100on a top surface 220. Preferably, the sensor codes are bar codes 230that communicate with a bar code reader (shown as second optical sensor410 in FIG. 4) within the cartridge receptacle 120.

[0033] The test strip 200 is exposed through the submerged openings ofthe cartridge 210 to provide an application region 260 in proximity tothe back end 290, and an assay region 250 in proximity to the front end215. The assay region 250 is dimensioned with respect to the cartridgereceptacle 120 so that a portion of the cartridge 210 containing theapplication region 260 extends from the reader 100 when the cartridge210 and reader are coupled. A sample may be deposited onto the teststrip 200 at the application region 260 to transfer by lateral flow tothe assay region 250. A protective layer (not shown) over the assayregion 250 protects the sample and chemical constituency of the stripfrom contamination and evaporation.

[0034] The sample deposited on the test strip 200 may comprise analytes.The term, “analyte,” as used herein, refers to the molecule or compoundto be quantitatively determined. Examples of analytes include proteins,such as hormones and other secreted proteins, enzymes, and cell surfaceproteins; glycoproteins; peptides; small molecules; polysaccharides;antibodies (including monoclonal or polyclonal Ab); nucleic acids;drugs; toxins; viruses or virus particles; portions of a cell wall; andother compounds possessing epitopes. The analyte of interest preferablycomprises an immunogenic portion, meaning that antibodies (as describedbelow) can be raised to that portion of the analyte of interest.

[0035] In a preferred embodiment, the test strip 200 may also comprise apopulation of first analyte binding agent, and optionally an analytenon-specific agent, coupled to a detection agent. In another preferredembodiment, the test strip 200 may also comprise two or morepopulations. For example, there may be a first population of firstanalyte binding agent coupled to a detection agent, and a secondpopulation of an analyte non-specific agent coupled to a detectionagent.

[0036] Analyte non-specific agent is defined as an agent non-specific tothe analyte of interest. The first analyte binding agents are agentsthat specifically bind to the analyte of interest. In a preferableembodiment, the first analyte binding agents are antibodies to theanalyte of interest. In another preferable embodiment, if the analyte ofinterest is an antibody of known specificity, the population maycomprise the antigen against which the analyte-antibody is directed. Theantibodies can be monoclonal antibodies or polyclonal antibodies. Theterm “antibody”, as used herein, also refers to antibody fragments thatare sufficient to bind to the analyte of interest. Alternatively, in apreferable embodiment, molecules that specifically bind to the analyteof interest, such as engineered proteins, peptides, haptens, and lysatescontaining heterogeneous mixture of antigens having analyte bindingsites, may also be used.

[0037] Different detection agents may be employed with differentpopulations of first and/or second analyte binding agents and analytenon-specific agent coupled to a detection agent. This situation mayarise, for example, when it is desired to assay two different analytesof interest on the same test strip. Use of two different detectionagents facilitates detection of the two different analytes of interest.For example, when the detection agent is a fluorescent agent, thedetection agents may be selected to fluoresce at different wavelengths.

[0038] In a preferred embodiment, the detection agent is a particle.Examples of particles useful in the practice of the invention include,but are not limited to, colloidal gold particles; colloidal sulphurparticles; colloidal selenium particles; colloidal barium sulfateparticles; colloidal iron sulfate particles; metal iodate particles;silver halide particles; silica particles; colloidal metal (hydrous)oxide particles; colloidal metal sulfide particles; colloidal leadselenide particles; colloidal cadmium selenide particles; colloidalmetal phosphate particles; colloidal metal ferrite particles; any of theabove-mentioned colloidal particles coated with organic or inorganiclayers; protein or peptide molecules; liposomes; or organic polymerlatex particles, such as polystyrene latex beads. Preferable particlesare colloidal gold particles. The size of the particles may be relatedto porosity of the membrane strip: the particles are preferablysufficiently small to be transported along the membrane by capillaryaction of fluid.

[0039] Colloidal gold may be made by any conventional means, such as themethods outlined in G. Frens, 1973 Nature Physical Science, 241:20(1973). Alternative methods may be described in U.S. Pat. Nos.5,578,577, 5,141,850; 4,775,636; 4,853,335; 4,859,612; 5,079,172;5,202,267; 5,514,602; 5,616,467; 5,681,775.

[0040] The selection of particle size may influence such factors asstability of bulk sol reagent and its conjugates, efficiency andcompleteness of release of particles from the test strip, speed andcompleteness of the reaction. Also, particle surface area may influencestearic hindrance between bound moieties.

[0041] The particles may be labeled to facilitate detection. Examples oflabels include, but are not limited to, luminescent labels; calorimetriclabels, such as dyes; fluorescent labels; or chemical labels, such aselectroactive agents (e.g., ferrocyanide); enzymes; radioactive labels;or radiofrequency labels. The number of particles present in the teststrip may vary, depending on the size and composition of the particles,the composition of the test strip and membrane strip, and the level ofsensitivity of the assay.

[0042] Also coupled to the detection agent may be a analyte nonspecificagent. This agent is selected for its ability to bind to substancesother than the analyte of interest. For example, if the analyte ofinterest is an antibody to H. Pylori, then the analyte nonspecific agentmay be an antibody to an antigen not found, or rarely found, in theantibody to H. Pylori. This binding may be specific for a substanceother than the analyte of interest or non-specific for such a substance.

[0043] In a preferable embodiment, the analyte non-specific agent may beantibodies, more preferably rabbit IgG. The antibodies can be monoclonalantibodies or polyclonal antibodies. The term “antibody”, as usedherein, also refers to-antibody fragments that are sufficient to bind tothe analyte of interest. Alternatively, preferably, molecules such asengineered proteins having non-specific binding sites nonspecific forthe analyte of interest, can also be used. In another embodiment, areceptor that non-specifically binds to ligands other than the analyteof interest can be used, and vice versa. Finally, the analytenon-specific agent may be an antigen, another organic molecule, or ahapten conjugated to a protein non-specific for the analyte of interest.Descriptions of other suitable analyte non-specific agents may be foundin U.S. Pat. No. 5,096,837, and include IgG, BSA, other albumins,casein, globulin, and immunoglobulin.

[0044] In a preferable embodiment, the analyte non-specific agentcomprises a control binding agent. Control binding agents are selectedso as to bind specifically to molecules other than molecules thatspecifically bind to the analyte of interest. In this way, these controlbinding agents can bind in control binding zones, as discussed below.Substances useful as control binding agents include those substancesdescribed above as useful as first analyte binding agents. In apreferable embodiment, the control binding agent comprises rabbitanti-dinitrophenol (anti-DNP) antibody. Additional beneficialcharacteristics of control binding agents include, but are not limitedto stability in bulk, non-specificity for analyte of interest,reproducibility and predictability of performance in test, molecularsize, and avidity of binding to the control agent.

[0045] One or more of the substances discussed above as suitable firstanalyte binding agents may be used as second analyte binding agents inone or more measurement zones on the strip 200. The measurement zone maybe either a control zone or an analyte binding zone. In a preferableembodiment, a second analyte binding agent is an antigen recognized bythe analyte of interest, which is an antibody. The second analytebinding agent may also be the antigen or even a second antibody specificfor the analyte (antibody) of interest. In another preferableembodiment, the analyte of interest is an antigen. The second analytebinding agent, which is an antibody, may be directed against a differentepitope of the analyte compared to the first analyte binding agent, whenthe latter is also an antibody. Alternatively, when the analyte is anantigen with multiple copies of the same epitope, the second analytebinding agent may be directed against the same epitope as the firstanalyte binding agent.

[0046] Control agents, present in the control binding zones, bindspecifically to the control binding agent to form a control bindingpair. Thus, control agents are those substances that may specificallybind to the control binding agents disclosed herein. A particularadvantage of the control binding pairs according to the invention isthat they are internal controls—that is, the control against which theanalyte measurement results may be compared is present on the individualtest strip. Therefore, the controls according to the invention may beused to correct for strip-to-strip variability. Such correction would beimpractical with external controls that are based, for example, on astatistical sampling of strips. Additionally, lot-to-lot, andrun-to-run, variations between different test strips may be minimized byuse of control binding agents and control agents according to theinvention. Furthermore, the effects of non-specific binding may bereduced. All of these corrections would be difficult to accomplish usingexternal, off-strip, controls.

[0047] During the assay, the analytes from the sample and the firstanalyte binding agent coupled to the detection agent may combine on thetest strip with second analyte binding agents in the measurement zones.This combination results in a concentration of compounds that mayinterrupt the continuous intensity of a signal arising from the teststrip 200. The compounds may be formed from a combination ofabove-mentioned analytes and reagents, including antibodies, detectionagents, and other particles associated with the analyte binding zoneand/or control zone. Based on the particular assay being performed, thecontrol binding zones may be selectively implemented to achieve anappropriate dynamic range which may be linear or nonlinear. Therespective quantitative values of the high and low control may in turnbe fitted to provide a standard curve, which may be used as acalibration parameter to determine a quantitative value for the analytebinding zone. Once the amount of control agent has been quantified (suchas in terms of Density of Reflection, discussed below), the amount maythen be mapped onto another more meaningful measurement scale, such asRelative Intensity (RI). The RI value may also be assigned concentrationvalues of analytes of interest. In this way, other meaningful unitsmeasurements such as number of copies of analytes present or theconcentration of analytes present may be read from the standard curve.Finally, signal to cutoff values (S/CO) above which cutoff values theassay result is considered positive may also be derived from the RIvalue.

[0048] During performance of the assay, a measurement zone may comprisea concentration of compounds that measurably affect a signal arisingfrom the strip after the sample is added to the strip. A signal mayarise when analytes present in the sample bind to a moiety comprised ofthe analyte binding agent and analyte non-specific agent coupled to thedetection agent, and are further caused to bind to second analytebinding agents and analyte non-specific agents coupled to the detectionagents present in the measurement zone to form concentrated regions ofcompounds. Still further, the compounds in the measurement zones mayalso be formed from combining a first population of analyte bindingagents existing on the application region 260 with an analyte in thesample, and/or combining the first population of analyte binding agentswith a second analyte binding agent existing on the assay region 250 ofthe test strip. The first population of analyte binding agents may alsoinclude control binding agents that bind with control agents in thecontrol zones once the sample is provided to the application region 260.

[0049] A detection zone is a region on the strip which contains one ormore measurement zones. The signal arising from the detection zonecorresponding to a concentration of compounds is termed a detectionsignal. A baseline is an approximation, or average, of the signalarising from any portion of the strip, excluding detection signals. In apreferred embodiment, the signal and detection signals of the strip arereflectance based measurements. As such, one or more measurement zonescontain concentrated quantities of compounds or complexes that formrelative dark regions against a highly reflective or substantially whitesurface of the test strip 200. In alternative variations, the detectionsignal may arise from alternative compounds such as those usingfluorescent or radioactive agents. In such instances, the signal of thebaseline may represent an average value of similar signal on the stripexcluding regions containing the measurement zones. In any variation,sensors within the reader 100 may be used to measure the detectionsignal arising from the measurement zones relative to the baseline.

[0050] As will be described in greater detail, the present inventionimproves over the known art by determining the baseline across one ormore detection zones of the strip in the presence of variations in thebackground signal. Each detection zone is preferably located such thatan automatic or semi-automatic analytical instrument, or a human reader,may determine certain results of the lateral flow assay. Once thebaseline in each detection zone is determined, the measurement zones maybe quantified and/or compared with respect to the baseline. Values ofthe measurement zones corresponding to the respective concentration ofcompounds may then be compared with one another to detect the presenceof antigens in sample.

[0051] In a preferred embodiment, the test strip 200 is formed from ahigh binding membrane having a substantially white reflectivebackground, including films such as nitrocellulose. If present, theanalytes in the sample react with first analyte binding agent coupled toa detection agent, and with second analyte binding agents in the analytebinding zones of the assay region 250 to give rise to compounds in afirst measurement zone. The compounds are light absorbing compounds thataffect the overall reflection intensity of the assay region 250.Preferably, the addition of the sample carries from the applicationregion to the assay region 250 control binding agents coupled todetection agents that combine with control agents in the control bindingzones. In a specific application, the addition of the sample carriesfrom the application region 260 the analyte binding agent and analytenon-specific agent bound to the detection agent and further combineswith control agents in the control binding zone. In this manner, themeasurement zones corresponding to the control binding zones eachcontain a relatively known quantity of the light absorbing compoundsthat create a second and third measurement zone. The reflective surfaceof the strip 200 detecting regions excluding the effect of themeasurement zones is the baseline of a preferred embodiment. Values maybe assigned to the measurement zones formed from the control and/oranalyte binding zones based on the intensity of reflection of therespective measurement zone with respect to the baseline. In a preferredembodiment, the values of the measurement zones forming a high and lowcontrol zone are normalized to a predetermined value, such as one andthree. A relative intensity curve may then be lifted between the valuesof the high and low control binding zones, as opposed to a standardcurve which uses the absolute unit value of the high and low control.The concentration of light absorbing compounds in the measurement zoneof the analyte binding zone may then be quantified by placing the valueof the reflection intensity onto the relative intensity curve defined bythe high and low control values. The presence of analytes that are thesubject of the assay may be indicated when the concentration value ofanalytes in the measurement zone of the analyte binding zone exceeds thecut-off value implemented with the assay.

[0052] Under this invention, the sample may include whole blood, serum,plasma, urine, or other biological samples associated with performingassays on humans. The invention may also provide for non-human samples,including samples originating from livestock or food products, as wellas veterinary samples. The analytes present on the test strip 200 andthe compounds formed with the sample depend in part on the type ofsample provided.

[0053] The test strip 200 of a preferred embodiment provides fivemeasurement zones comprised from three analyte binding zones and twocontrol binding zones. Each analyte binding zone may be implemented toindicate the presence of analytes to such diseases such as H. pylori,AIDS, herpes, and hepatitis. Greater or fewer analyte binding zones orcontrol binding zones are also contemplated by this invention. Apreferred embodiment may also be employed to detect the presence of foodcontamination, such as E. Coli or Salmonella.

[0054]FIG. 3 is a block diagram showing general components of the reader100. The computer system of a preferred embodiment is shown to comprisea processor 300 having memory resources 310. As will be described ingreater detail, the memory resources 310 stores a plurality of assaytables, with each assay table having parameters and fields suited for aparticular assay. The processor 300 receives parameters from the memoryresources 310 and executes an algorithm for controlling and analyzingthe assay. The processor 300 may also receive parameters or prompts fromthe input device 390, which may include a keyboard 130, or othersuitable devices. An output 385 may prompt the user for information orprovide the results of the assay. The output 385 may include the display140, or a printer, or other audio/visual devices. The processor may alsoreceive input information or provide output information through a serialport 395. The serial port 395 may comprise an infrared port fortransferring information between the reader 100 and an externalcomputer, but may also include other known serial ports such as a pinconnector or modems. Information that may be provided to the computersystem may include parameters that reconfigure the assay tables of thememory resources. The information may be provided through the inputdevice 390, serial port 395, or alternatively through a replacementmemory chip such as an insertable memory chip.

[0055] As shown by FIG. 3, a preferred embodiment provides that theprocessor 300 is linked via an analog-digital converter 320 to a firstand second sensors 340 and 330. The analog-digital converter 320converts analog signals from the optical sensors into voltage counts forthe processor 300. In alternative embodiments, the analog-digitalconverter converts signals from a sensor that detects alternativedetection signals, such as fluorescence, radiation, magnetic flux, orany other detection signal detectable with a sensor. One of the sensorsmay be used to input information to the computer system that iscontained on detectable codes on the surface 220 of the cartridge 210.In a preferred embodiment, the first and second sensors are lightsensors for measuring the reflection intensity arising from the strip200. As such, a preferred embodiment may include a light source 350 thatenhance the detectable reflectance arising from the strip. The processor300 may couple to a heater 380 that heats the sample to a predeterminedtemperature, thereby increasing the accuracy and speed of the assay. Aswill be explained below, the processor 300 controls the temperature andincubation time for the assay. In this manner, the assay may be heatedat an optimal temperature and duration. A motor 370 also couples to theprocessor and provides a preferred mechanism for scanning the first andsecond sensors 340 and 330 across the test strip 200 and/or cartridge210.

[0056]FIG. 4 is a front view of the reader 100 detailing a preferredembodiment of the invention. As shown by FIG. 4, the cartridgereceptacle retains the cartridge 210 in position to access the teststrip 200 (of FIG. 2) to the associated components. The cartridgereceptacle 120 also includes a top printed circuit board 480 and a leftsidewall 470 and a right side wall 430. The top printed circuit board480 and sidewalls 470 and 430 may combine to cover and protect the assayregion 250 of the test strip 200 from contamination or unwanted elementsthat may otherwise affect the performance of the assay. A first opticalsensor 420 extends from the top printed circuit board 480 of thecartridge receptacle 120 and aligns over the assay region 250 of thetest strip 200. The first optical sensor 420 measures the reflectivityof the assay region 250 once the assay is initiated. The light sourcemay be used with either optical sensor to illuminate the test strip 200.A second optical sensor 410 may be used to read bar codes 230 providedon the top surface 220 of the cartridge 210 (as shown by FIG. 3). FIG. 4shows that the first optical sensor 420 and second optical sensor 410 ofa preferred embodiment are vertically offset with respect to one anotherto compensate for the elevation difference between the bar code 230 onthe cartridge and the assay region 250 exposed within the cartridge. Thecartridge receptacle 120 may mount to a bottom printed circuit board 460to couple the components contained therein with the computer system.

[0057]FIG. 4 further shows a first pad 440 and second pad 450 positionedon the bottom printed circuit board 460 to form an autostart trigger400. As will be discussed in greater detail, the autostart trigger 400is coupled to the computer system 300 (FIG. 3) and associated circuitryto detect the presence of the first drop of the sample deposited on theapplication region 260. Among other advantages, the autostart trigger470 improves in part over the prior art in it enables a coupled timer toinitiate at an exact moment when the sample is deposited on theapplication region 260.

[0058]FIG. 5 is a front isometric view of the cartridge receptacle 120further detailing the components therein. As shown, the cartridgereceptacle 120 includes a front opening 570 for receiving the cartridge210, and a back end 560. A left and right receiving structure 515 and525 for receiving the cartridge 210 extends from the front opening 570to the back end 560 and in close proximity to the bottom printed circuitboard 460. The receiving structures are precisely dimensioned tofrictionally fit the front end 215 of the cartridge 210 (as shown byFIG. 2).

[0059] The cartridge receptacle 120 preferably includes a motionmechanism for moving a first optical sensor 420 with respect to the teststrip 200. To this end, a left and right rail 510 and 520 each mount toa top portion of the respective left and right sidewall 470 and 430, andextend in a longitudinal direction defined by the front opening 570 andback end 560. A sled 530 slidably mounts over the left rail 510 andretains the top printed circuit board 480 that extends to the right rail520. The first optical sensor 420 and second optical sensor 410 attachto the top printed circuit board 480 extending from the sled 530. Themotor 370 engages the sled 530 to longitudinally direct the sled alongthe rails 510 and 520. The resulting motion of the sled 530 moves thetop printed circuit board 480, so that the first optical sensor 420 andsecond optical sensor 410 also move longitudinally within the cartridgereceptacle 120. In this arrangement, the first optical sensor 420 andsecond optical sensor 410 move over the inserted test strip 200 inperforming the assay. This arrangement allows the test strip 200 toremain fixed when the sample is deposited to the application region 260and flows laterally from the application region 260 to the assay region250. Alternatively, the motor 370 may be coupled to the cartridge 210 tomove the test strip 200 with respect to the sensors. Preferably, thefirst optical sensor 420 communicates with the computer system through asingle element optical sensor, such as a phototransistor or photodiodedevice. However, multiple array optical sensors such as digital cameras,diode arrays, CCD arrays, or any other photosensitive imaging device mayalso be employed with this invention, although such multiple arrayoptical sensors add computation cost to the microprocessor.

[0060]FIG. 5 also shows that the cartridge receptacle 120 includes aheating element 540 for locally heating the test strip 200. Aspreviously mentioned, the timing and accuracy for performing the assaymay be significantly improved by heating the sample during the assay. Asshown by the embodiment of FIG. 5, the heating element 540 is a copperor metallic element having sufficient thermal conductive properties toconduct heat to a localized area of the test strip 200. In this manner,the heating element 540 provides for a rapid assay by heating the strip,but not the cartridge receptacle 120. As such, the heating element 540preserves battery life for field operations, while increasing the speedand accuracy of the assay.

[0061] The heating element may be controlled by coupling it to thecomputer system through associated circuitry (not shown). The associatedcircuitry may include a temperature feed back control circuit or othersensor, such as a proportional controller or PID controllers, toprecisely regulating the temperature of the heating element 540. Thecomputer system may provide the exact temperature and incubation timefor switching the heating element on and off. In this manner the heatingelement 540 may be operated at the optimal temperature and incubationtime for a particular assay. As will be described below, the optimaltemperature and incubation time for any particular assay may be providedby an assay table stored in the memory resources 310 of the computersystem. Accordingly, the heating element 540 of a preferred embodimentmay enhance the flexibility of the reader 100 to perform a wide range ofassays.

[0062]FIG. 5 further details the autostart trigger 400 of a preferredembodiment. The first pad 440 and second pad 450 that comprise theautostart trigger 400 may be any electrical lead, including metal platesor meshes. As shown, the first and second pads 440 and 450 may bemounted in co-planar fashion to the bottom printed circuit board 460.Preferably, the pads combine to form a capacitor, with each pad forminga capacitor plate. In alternative variations, the pads may combine toprovide a detectable electrical field that noticeably changes upondeposition of the sample. Upon entrance of the cartridge 210 into thecartridge receptacle 120, the test strip 200 is aligned so that an areaunder the assay region 250 contacts the heating element 540. Oncealigned, the application region 260 is in close proximity to the firstpad 440 and second pad 450. The alignment of the test strip 200 isillustrated by the region corresponding to numeral 580. Alternativevariations allow the positions of the first and second pads 440 and 450to be moved away from the bottom printed circuit board 460, as the padsmay be positioned anywhere relative to the strip 200 to allow thecapacitance or electrical field to be affected by the deposition of thesample. Similarly, the alignment of the pads may be non-coplanar, oreven perpendicular, as such alternative positions still produce anelectrical field that is affected by the deposition of the sample.

[0063]FIG. 6 is a block diagram that details the autostart trigger 400of a preferred embodiment. The first pad 440 and second pad 450 arearranged on the bottom printed circuit board 460 (FIG. 4) to couple withan electrical potential to form a sensing capacitor for detecting whenthe sample is deposited onto the application region 260 of the teststrip 200. The autostart trigger may couple to the computer systemthrough a sensory output line 640. The signal from the autostart trigger400 may be amplified prior to being received by the computer system. Asshown by a preferred embodiment of FIG. 5, the test strip 200 alignsover a portion of the first pad 440 and second pad 450, with the spacebetween the first and second pad being aligned over the centerline ofthe test strip 200 (as shown by FIG. 5). The test strip 200 is placed insufficient proximity to form a portion of the dielectric layer betweenthe capacitor formed by the first pad 440 and second pad 450.Alternatively, the first pad 440 and second pad 450 may abut the bottomportion of the test strip 200. In this arrangement, the first pad 440and second pad 450 may be coupled to a current source 610 that causesthe voltage on the sensing pads to ramp up. A switch 620 may be coupledto the current source 610 to allow the sensing pads 440 and 450 todischarge periodically. The voltage on the first pad 440 and second pad450 signal a sawtooth waveform, with an average value related to thecapacitance between the first and second sensing pads 440 and 450. A lowpass filter 630 may be coupled to generate the average value of thevoltage on the sensing pads 440 and 450. Prior to the time the sample isdeposited, the application region 260 is dry and the dielectric constantformed in part by the test strip 200 is low. When the sample is appliedto the application region 260, the dielectric constant is significantlyincreased, causing a change in the capacitance between the sensingplates. A software algorithm executed by the computer system may then beused to compare the curve of the capacitance versus time across thefirst pad 440 and second pad 450 to detect the presence of a samplebased on a threshold change in the capacitance curve. In alternativevariations, depositing the sample induces a change in the electricalfields between the electrical leads. In this manner, the autostarttrigger 400 may detect the change in capacitance of the first pad 440and second pad 450 upon addition of the sample to the application region260 of the test strip 200. Once the sample is detected by the autostarttrigger 400, the computer system initiates timing the assay. Timing theassay allows the assays to be analyzed by the sensors and processor atan exact moment after the sample is deposited. As such, the reader 100provides an advantage over the known art in that it avoids inaccuraciesthat result from mis-timing the moment at which the final analysis ofthe test strip 200 is performed.

[0064] Several alternative methods for detecting the change in thecapacitance of the pads 440 and 450 exist. For example, the first pad440 and second pad 450 may be used to form a capacitor element of aninductor-capacitor (“LC”) circuit. The LC circuit may be coupled to anoscillator, and associated circuitry may then be implemented to sensethe change in capacitance when the fluid sample is added to theapplication region 260.

[0065] In alternative embodiments of the present invention, an autostarttrigger may be coupled to or comprises within the reader 100′ of thepresent invention to detect any physical change arising from depositingthe sample on the strip. For example, sensors may be coupled to theprocessor to detect changes in the surface tension of either the strip200 or of the sample being deposited on the strip. Alternatively,sensors may also couple to the strip to determine the conductivity ofthe strip before and after the sample is determined. Such sensors mayinclude implementing a voltage potential on one end of the applicationregion 260, and determining the current or voltage on another end of theapplication region before and after the deposition of the sample to thestrip 200. Other alternative variations for autostart triggers may befound in the prior art, such as U.S. Pat. No. 5,554,531 to Zweig, andU.S. Pat. No. 5,580,794 to Allen, both of which are hereby incorporatedby reference.

[0066] In a preferred embodiment, the autostart trigger 400 generates acontinuous waveform that is affected by any change in the dielectriclayer or electric field shared between the sensor pads 440 and 450. Forexample, insertion of the cartridge 210 may interfere with thedielectric layer or electric field between the sensor pads to cause theresulting waveform to change sufficiently to falsely indicate thepresence of a sample. Therefore, a preferred embodiment also includes amechanism that prevents the autostart trigger 400 from signaling theprocessor until a time delay period after the insertion of the cartridge210. In a preferred embodiment, the mechanism includes an infraredsensor mounted within the cartridge receptacle 120 that signals thecomputer system upon insertion of the cartridge 210. The processor 300may be programmed or otherwise provided with resources to preclude theautostart trigger from signaling the processor of a capacitance changefor a time delay period after the insertion of the cartridge 210. Thetime delay is preferably shorter than the minimum time needed by a userto deposit the sample after the cartridge is inserted. In this manner,the insertion of the cartridge will not falsely signal the processor toinitiate the timer for the assay. Rather, the time delay ensures thatthe timer for the assay will not be signaled until the sample isdeposited.

[0067] As noted, the reader 100 includes resources such as the processor300 and memory resources 310 that retain parameters and information forcontrolling and analyzing the assay. The parameters and fields may bestored in the memory resources 310, and include fields for performingthe algorithm that analyzes and interprets the results of the assay. Thefields and parameters may be grouped into assay tables, which may beselected according to the particular assay being performed. In thismanner, the assay table encodes any combination of fields and parametersfor analyzing distinct assays, as well as including fields andparameters to correctly analyze each assay. The assay tables may bereconfigured to provide one or more updated parameters for assays, or toinclude additional assay tables for new assays. The assay tables may bereconfigured by a combination of the input device 390, serial port 395,and replaceable memory resources 310. Thus, the assay table may bereconfigured in any number of ways, including modifying a single elementthrough the bar code on the cartridge 210 or by uploading an entirelynew assay table. A preferred embodiment employs Dallas Buttons as memoryresources, which may be easily removed or added to a compartment orsurface of the reader 100.

[0068] In more detail, the memory resources 310 of a preferredembodiment may include the following parameters as fields included inthe assay tables:

[0069] ZONELOCATION: This field identifies the location or relativeposition of the measurement zones on the test strip 200. The field ispreferably 15 bits, with each 3 bits identifying a particularmeasurement zone. The measurement zones may be selected to correspond toeither analyte binding zones or control binding zones, thereby allowingthe respective zones to be positioned anywhere on the test strip 200with respect to one another. A preferred embodiment stores fivemeasurement zones on the strip, including measurement zones for threeanalyte binding zones and two control binding zones. The control bindingzones may be high or low control, while each analyte binding zone mayinclude an analyte for one or more assays. The ability of the reader toallow for selection of the position of the measurement zones for thecontrol binding zones and analyte binding zones is particularlyadvantageous, since the presence of an upstream measurement zone mayaffect the chemical constituency of a downstream measurement zone duringlateral flow. Therefore, the optimal relative position of the controlbinding zones and the analyte binding zones may differ from assay toassay. A preferred embodiment provides flexibility in ensuring thecontrol and analyte binding zones may be positioned in their optimalposition on the test strip 200 for any particular assay.

[0070] HIGHCONTROL/LOWCONTROL: These fields specify relative values ofthe detection signal arising from the high and low control bindingzones. The values from these fields may be assigned from the assay tableto the algorithm.

[0071] ASSAYID: The particular assay table to be employed for the assayis specified by this field. The field is preferably specified from thebar code on the cartridge 210 carrying the test strip 200.

[0072] MAXCONTROLRAT/MINCONTROLRAT: These fields specifies the maximumand minimum ratio between the measurement zones corresponding to thehigh and low control binding zones.

[0073] METHODSIZE: This field determines the method for interpreting theresults of the assay, and the sample size to be used in the assay.Preferably, the processor 300 internally determines the results of theassay by using a relative intensity curve. Based on the value of thisfield stored or inputted into the assay table, the results may then bedisplayed to the user using either signal cut-off value, standard curve,or the relative intensity curve. With the standard or relative intensitycurve, the detection signal arising from the measurement zone of theanalyte binding zone is quantified from the curve, and then compared tothe cut-off value to determine if sufficient analytes exist for apositive reading. The detection signal arising from the measurement zoneof the analyte binding zone is divided by the cut-off value to determinethe signal-cut-off value. The ability to select or predetermine themethod for interpreting any particular assay further enhances theflexibility provided to the user by the reader 100.

[0074] KINITICSTARTTIME: This field may be used to specify the timeinterval beginning with the addition of the sample until the first readoccurs.

[0075] ASSAYTIME: This field specifies the total assay time in seconds.

[0076] ASSAYTEMP: This field specifies the preferred temperature forrunning a particular assay.

[0077] LOWCONTROLMINDR/LOWCONTROLMAXDR: These fields specify the minimumand maximum low control values quantitatively. In a preferredembodiment, the fields are expressed in terms of Density of Reflection(DR), as further described below. If the low control is either belowLOWCONTROLMINDR or above LOWCONTROLMAXDR, an error will be provided.

[0078] CUTOFFRATIO: This field specifies the cutoff ratio used todetermine whether a given measurement zone of an analyte binding zone ispositive or negative. This field may be provided in the assay as apredetermined value based on laboratory experimentation. In a preferredembodiment, the field may be altered by the bar code, which provides amultiplication factor for the value of the field stored in the assaytable. Alterations in the bar code may then change the cut-off value. Assuch, the assays are not limited to a strict cut-off value, but rathermay provide cut-off values as a variable input to the algorithm. Thisenables the cut-off values to be altered as the need arises.

[0079] The processor 300 uses the assay tables of the memory resources,as well as parameters and fields inputted through the input device 390and/or serial port 395, to execute an algorithm that accurately analyzesand interprets the results of the assay. The processor may also receiveprompts or input information for running the algorithm from the barcodes 230 via the second optical sensor 410.

[0080]FIG. 7 describes a preferred algorithm performed by the processor300 in determining the results of the lateral flow assay. The algorithmof this invention analyzes the results of the lateral flow assay bygenerating a baseline, quantifying the measurement zones with respect tothe baseline, and then comparing measurement zones corresponding to thecontrol binding zones and analyte binding zone. The baseline isgenerated to approximate the signal of the strip 200 as if themeasurement zone is not present. In order to attain the most accurateresults for a preferred embodiment, the baseline should approximate thereflectance of the test strip 200 after the assay has been performed.However, the baseline of the actual test strip 200 after the performanceof the assay is not constant across the strip. Rather, several factorscontribute to produce an uneven or spotty baseline. For example, whenperforming an assay by measuring the reflectance arising from the strip,the reflectance of the baseline may be affected by (1) wave frontscreated by the sample which create patches of wet and dry regions alongthe length of the strip; (2) nonspecific binding, which results in theformation of light absorbing particles in between the measurement zones;(3) warpage in the nitrocellulose layer; and (4) manufacturing problemsin implementing a flat test strip 200 within the cartridge 210. Inaddition, when whole blood is used as the sample, the baselinereflection may be affected by red blood cells or hemogloblin.

[0081] In several examples provided by the known art, these problemshave been avoided by generating a baseline from a dry strip, orinputting the baseline as a known constant into a calculation forevaluating measurement zones. These approximations for the baseline asdetermined by the known art lack accuracy, however, as theapproximations are not from the strip after undergoing the assay. Thus,the baseline incorporated for interpreting assays in the known art failto account for example, ripples that actually change the reflectance ofthe strip and thereby affect the results of the assay. Similarly, theknown art fails to account for measurement zones containing compoundsformed after the sample is deposited on the strip.

[0082] Among other advantages, this invention improves in part over theknown art by approximating a baseline from the test strip 200 after theassay is performed. The resulting approximation is considerably moreaccurate for evaluating the measurement zones and comparing themeasurement zones to one another. In a preferred embodiment, thealgorithm generates the baseline by approximating a relatively flatbaseline in detection zones where the intensity of reflectance of thestrip is variable with respect to the background of the strip. Inparticular, the detection zones include measurement zones correspondingto the control binding zones and/or analyte binding zones, which containconcentrated amounts of light absorbing compounds. The algorithm thenuses the baseline to quantify or evaluate the measurement zones withrespect to the baseline, and then compares the value of each measurementzone to determine the presence of disease. In a preferred embodiment,the measurement zones are quantified by using the baseline to determinethe Density of Reflection (DR) of the measurement zone. Alternatively,the measurement zones may be quantified through equations or functionsthat compare the detection signal arising from the measurement zone withrespect to the detection signal arising from the remainder of the teststrip. The measurement zones may also be evaluated qualitatively withrespect to the baseline, or mapped using the baseline to determine theresults of the assay.

[0083] In step 700 of the algorithm, the first optical sensor 420 scansor views the test strip 200 and compiles an array of raw data RAW thatcorresponds to the intensity of the reflectance of the strip.Alternative embodiments of this invention may provide for a sensor thatdetects detection signals such as fluorescence or radiation. In eithercase, the array RAW represents voltage counts of the analog-digitalconverter which may be coupled to the sensor of the particular variationto reflect the intensity of the alternative detection signals. In asuccessful assay performed under a preferred embodiment that measuresreflectance from the strip 200, the measurement zone of the high controlzone is relatively darker or less intense in reflectance than themeasurement zone of the low control zone due to a greater concentrationof light absorbing particles. One or more measurement zones of analytebinding zones may also be present, depending on whether the samplescontained analytes. As such, the darkness or reflectance intensity ofthe analyte binding zones is a variable measurement zone. The array RAWrecords the reflectance intensity arising from the strip, including thereflectance of the measurement zones. The array RAW is then filtered bya low-pass filter that represents a moving average of the array RAW. Thefiltered data is retained in the array FILT.

[0084] Step 720 shows that a Boolean operation assigns a binary state tothe individual elements of FILT. In a preferred embodiment, the Booleanoperation is designed to approximate the proximity of the individualarray element to an average white reflectance. When the state assignedby the Boolean operation is “true”, the individual elements of FILT aretermed “white”. For purposes of this disclosure, “white” refers toelements that fall within a range of threshold approximations of theaverage white for the strip. When the Boolean operation is “false”, theindividual elements of FILT are “dark”. The term “dark” refers toelements that are not white, or false under the Boolean conditionprovided above. Numerous operations may be used with this invention toassign the binary state to the elements of FILT. For example, theBoolean operation may reflect a substantial change between thereflection intensity of adjoining points or a selected block of points.

[0085] In a preferred embodiment, the Boolean operation-is modeled aftera non-linear decay circuit comprising a diode-resistor-capacitor, asshown by a circuit 725 in FIG. 7a. The charging voltage on the capacitormay be modeled after the following equations:

Vout _(i+1)=(Vout+Vin)_(i)/2  (1)

[0086] for a charging capacitor; and

Vout _(i+1) =Vout _(i) −Vout _(i)*(1/DF)  (2)

[0087] for a decaying capacitor.

[0088] In the above equations, DF represents an exponential or highorder decay factor. The value of DF is preferably chosen to match thedegree of ripple or other defect observed in actual strips. Large valuefor DF are appropriate for “good” strips which have fewer ripples, andprovides for the best detection of small signals. Smaller values for DFreject larger defects at the expense of reduced ability to distinguishsmall signals from the baseline. In this model, Vin is provided by FILT,and an array NONL stores Vout. Under a preferred embodiment, whenequation (1) is true, elements of FILT are assigned a “white” state inCHG and equation (1) applies in determining NONL. If equation (1) holdsto be false, then the elements of FILT are assigned a “dark” state inCHG, and equation (2) applies in determining NONL. Once the CHG and NONLarrays are determined, the array BASE representing the baseline may beformulated. Initially, BASE is set to zero in step 730.

[0089] The subroutine 800 generates the baseline approximation fordetection zones on the strip based on the information stored in FILT,CHG, and NONL. The first step 810 calculates the derivative of FILT withrespect to BASE and stores the values in an array DERIV1. The next step820 calculates the derivative of DERIV1 with respect to BASE and storesthe values in an array DERIV2. In step 830, ail maximas and minimas aredetermined from DERIV1 and stored in an array MAXIM. The elements ofMAXIM may be either local maximas/minimas or endpoints to measurementzones that correspond with array elements of FILT. In addition,individual elements of CHG, DERIV1, and DERIV2, correspond to the sameelements of FILT.

[0090] The algorithm then identifies in step 840 a beginning point toeach measurement zone present on the strip. Step 845 of a preferredembodiment shows than an element of MAXIM is a beginning point of ameasurement zone if it immediately precedes or is at a location whereCHG switches from “white” to “dark”. This criteria ensures that themaxima is a beginning point to a measurement zone as opposed to a localmaxima or a minima. By properly choosing the DF, most of the localmaximas and minimas may be removed from FILT. Once a beginning point isfound, step 850 seeks the ending point of the measurement zone by firstidentifying an element of MAXIM where CHG changes states from “dark” to“white”. The algorithm then implements a criteria for determining asubsequent point in a “white” state that is an endpoint to themeasurement zone. The criteria may include steps 860 and 870, whichdetermines whether a first and second derivative threshold is met by anelement of MAXIM subsequent to the point found in step 850. The firstand second derivative thresholds may be implemented as predeterminedconstants.

[0091] Once the endpoint to the measurement zone is found, the algorithmin step 880 interpolates between the beginning and ending points of themeasurement zone. The interpolation may be accomplished by connectingthe beginning and ending points through a straight line or through someother function that approximates a baseline between the two points. Thealgorithm also interpolates a baseline in the detection zonesencompassing points beyond the measurement zone. Interpolation in thedetection zones may be accomplished by connecting the respective maximasand minimas outside of the measurement zone. All interpolated points maythen be stored in BASE.

[0092] In a preferred embodiment, anywhere between two to fivemeasurement zones may be present on the test strip 200. In step 885, thealgorithm checks to see whether all data in FILT has been checked toensure all measurement zones are located. If additional points arepresent, the algorithm returns to step 850 to determine whetheradditional measurement zones exist on the test strip 200. When allvalues of FILT have been checked, step 890 performs a max BASE withNONL, where corresponding elements of the two arrays are compared, andBASE receives the greater of the two elements. This step serves asanother approximation to the baseline generated by the subroutine 800.

[0093] The approximation of the baseline may be improved by repeatingsteps 810 through 890 again, except in the subsequent loop BASE is anapproximation of the average baseline of the strip, rather than “0”. Thesecond approximation of the baseline differs in that DERIV1 and DERIV2may be calculated with respect to BASE having values of the averagebaseline. The resulting baseline is a much smoother approximation of theaverage baseline for the strip. The subroutine for determining thebaseline may be repeated a number of times, but beyond two iterationsyields insignificant improvements.

[0094] Once the baseline is generated, the algorithm then proceeds todetermine the reflection intensity of the strip in subroutine 900 byusing FILT and BASE. In step 910 reflection intensity may be calculatedby determining the DR, represented by the following formula:

DR=log [(FILT−BLACK)/(BASE-BLACK)]

[0095] BLACK may be an array of constants that correspond to thereflection of the strip when the light within the cartridge receptacleis turned off. In a preferred embodiment, the DR is calculated only forminimas between each pair of maximas. This allows for the use of a smallprocessor for field uses of the reader. Alternatively, the DR of everyelement of FILT may be determined with larger processors. In variationsof the invention, the difference between the intensity of the detectionsignal and the baseline may be evaluated using different formulas andcriteria. The equation provided above is preferred for reflectance basedassays.

[0096] In step 920, DR for each determined measurement zone is checkedagainst preselected limits stored in the assay table. This step mayinclude checking parameters such as HIGH CONTROL and LOWCONTROL,MAXCONTROLRAT and MINCONTROLRAT, as well, as other parameters that mayindicate an error in the assay. The spacing between measurement zones isalso checked to conform to the preselected spacing, which in a preferredembodiment is retained in the assay table as MINBANDSPACING andMAXBANDSPACING.

[0097] Valid measurement zones are detected in step 925 and recorded instep 930 as a separate sequence. Once all valid measurement zones arerecorded, the algorithm checks in step 940 for gaps in the sequence.Instances when gaps may be found include when the sample that lackantigens, i.e. where the assay is negative. If a gap is found in step945, the gap is interpolated over and added to the table of measurementzones in step 950. The algorithm stops in step 960 once the number ofdetected measurement zones and gaps matches the number of measurementzones expected by the input to the reader 100. Otherwise, steps 910-960are repeated.

[0098]FIG. 8 illustrates a graph of values generated by the algorithm ofa preferred embodiment, detailing the generation of the baseline and theevaluation of the measurement zones for the control and analyte bindingzones with respect to the baseline. Curve A is derived from FILT, and isa quantified representation of the strip in terms of the voltage countdetected from the A/D converter. While the voltage counts of curve Arepresent reflection intensity arising from the strip, in alternativeembodiments, the voltage counts may represent the intensity of anydetection signal arising from the strip. In a preferred embodiment,brighter or more reflective surfaces produce a higher count on the graphpresented in FIG. 8. In region I, curve A shows the first optical sensor420 as being away from the test strip 200. In region II, the opticalsensor scans a shadow region formed by the edge of the exposed teststrip 200 and the cartridge 110. The shadow region may be used by theprocessor to synchronize the first optical sensor 420 with the locationof the measurement zone for the control and/or analyte binding zones.The values of DERIV1 are generally greater in the shadow region due tothe lack of reflection. Once the derivative of curve A is determined toexceed a predetermined threshold value corresponding to the slope of theshadow region, the position of the optical sensor is then marked as thebeginning of the test strip 200.

[0099] Region III of curve A contains a measurement zone Z1 present onthe test strip 200. The algorithm detects the beginning point Mx11 andending point Mx12 of the measurement zone Z1. Each beginning and endingpoint is contained within region III and just outside the measurementzone Z1, where the reflection of the measurement zones become noticeablydifferent than the average background reflection. As illustrated bycurve A, the beginning point Mx11 is a maxima on the curve A that issubsequently followed by curve A changing from a “white” state to a“dark” state. As previously noted, the change of state is stored in CHG.A minima Mi11 is the point between the beginning and ending points Mx11and Mx12, and represents an area of the measurement zone having theleast reflection or lowest-count. The maxima Mx12 follows curve Achanging state from “dark” to “white” and meets the threshold test ofsteps 860 and 870 of the algorithm of FIG. 7. Curve B shows a baselinegenerated from the algorithm of a preferred embodiment to furtherquantify curve A. The baseline matches the filtered points of curve Aoutside of the measurement zone Z1. Inside the measurement zone Z1, afunction connects the beginning and ending points Mx11 and Mx12 to formthe baseline. Preferably, the function is a straight line between thetwo points, although other functions may be used.

[0100] Regions IV and V produce measurement zones Z2 and Z3,corresponding to additional measurement zones present on the strip. Aswith measurement zone Z1, the baseline represented by curve B may beinterpolated between beginning points Mx21, Mx31 and ending points Mx22,Mx32 of respective measurement zones Z2 and Z3. Likewise, eachmeasurement zone Z2 and Z3 includes a minima Mi22, Mi33 which representsthe area of the respective measurement zone having the least reflectiveproperties.

[0101] As shown by FIG. 8, measurement zones Z1 and Z2 correspond tohigh and low control binding zones on the test strip, and measurementzone Z3 corresponds to the analyte binding zone. A preferred embodimentmay be employed with the assay tables stored in the memory resources 310to provide flexibility in performing the assay and analyzing theresults. In particular, the location of the particular zones may becontrolled by ZONELOCATION, so that measurement zone Z1 or Z2 mayalternatively represent the analyte binding zone. The values ofmeasurement zones Z1 and Z2 may be controlled by HIGHCONTROL andLOWCONTROL. The ratio between Z1 and Z2 may be limited by MAXCONTROLRATand MINCONTROLRAT. The field SPACING may be used to provide for therelative distance between the measurement zones.

[0102] Curve C represents curve A quantified with respect to curve B. Ina preferred embodiment, curve C is determined by approximating the DR inthe measurement zones, using values of curve A corresponding to FILT andcurve B corresponding to BASE. The DR of each measurement zone may bedetermined by determining the DR of the minima for each measurementzone. Alternatively, the DR for each element of FILT represented bycurve A may be determined with respect to curve B and BASE. The outputmay be represented through a relative intensity curve. In FIG. 8, theratio of values for the high and low control represented by measurementzones Z1/Z2 is approximately three. The value of the measurement zone Z3representing the analyte binding zone is determined relative to thevalues for the measurement zones Z1 and Z2. In this method, the valuesof the respective measurement zones may be determined in terms of RI.

[0103] In a preferred embodiment, the reader 100 will provide a“positive” result to the user if the value of measurement zone Z3representing the analyte binding zone is greater than the cut-off value.The cut-off value may be altered between the assays by multiplyingCUTOFFRATIO by a factor inputted into the processor 300 by the bar codeor other input device.

[0104] From the above description, the algorithm of a preferredembodiment may include (1) a peak detector based on digitalimplementation of a Boolean function, such as the analog diode-RCcombination shown in FIG. 7a; (2) a non-linear interpolation of maximausing information from the first and second derivatives, where theinformation is derived from raw data recording the intensity ofdetection signals arising from the strip 200; and (3) repeating step (2)for further accuracy.

[0105] While a preferred embodiment may use the methods presented above,other methods may also generate a baseline across a test stripundergoing or having undergone an assay. In general, other methodspresented below have fewer advantages than the methods described above,in that the methods below may require additional computational costs,lack precision, and may be limited in applications or diversity. Theseother methods may include employing a peak detector to detect themaximas/minimas of the data representing the detection signals from thetest strip 200, where the peak detector is symmetrically employed toevaluate the values of the detection signal in a first direction acrossthe strip, and then employed again to evaluate the values of thedetection signals in the reverse direction to the first direction acrossthe strip. Such a filter is more appropriate when the data representingthe values of the detection signal is symmetrical with respect to afront and back end of the assay region of the strip 200. Such a peakdetector would no longer require an array such as CHG, because theBoolean values stored in that array lack the asymmetry that requires theuse of first and second derivative thresholds to disambiguate thelight/dark transitions. A change to a symmetric filter would eliminatesome steps in the non-linear interpolation, and achieve comparableresults at the expense of modest increases in computational complexity.

[0106] Several other classes of filter are also possible which do notrequire an “analog” circuit model as described elsewhere in theapplication. In addition, an interpolation step based on “peaks” fromthe peak detector rather than “maxima” is possible. Such aninterpolation would be sub-optimal, as it would tend to over-estimatethe baseline and thus over-estimate the DRs when the general trend ofthe data is rising or falling. However, one possible advantage of such amethod would be to avoid the use of derivatives entirely.

[0107] Still further, other variations to a preferred embodiment usingthe methods described above for generating a baseline include using apeak minima when excessive band widths are encountered to detect a peakpair where the gap between peaks does not return to the baseline. Thisstep may be employed by providing a table of minima from the firstderivative to be assembled.

[0108] The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in this art.The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. A method for performing a lateral flow assaycomprising: a. depositing a sample on a test strip at an applicationregion, the test strip including a first detection zone with a firstmeasurement zone; b. detecting a first detection signal arising from thefirst detection zone; and c. generating a baseline for the firstdetection zone by interpolating between values of the first detectionsignal outside of the first measurement zone and inside of the firstdetection zone.
 2. The method of claim 1, wherein the first measurementzone comprises a concentration of compounds that affect an intensity ofa signal arising from the test strip, the compounds being formed afterthe sample is deposited on the test strip.
 3. The method of claim 1,further comprising locating a beginning boundary and an ending boundaryfor the first measurement zone on the test strip.
 4. A method forperforming a lateral flow assay comprising: a. depositing a sample on atest strip at an application region, the test strip including a seconddetection zone within a second measurement zone; b. detecting a seconddetection signal arising from the second detection zone; and c.generating the baseline for the second detection zone by interpolatingbetween values of the second detection signal outside of the secondmeasurement zone and inside of the second detection zone.
 5. The methodof claim 4, wherein the second measurement zone comprises aconcentration of compounds that affect an intensity of a signal arisingfrom the test strip, the compounds being formed after the sample isdeposited on the test strip.
 6. The method of claim 4, furthercomprising locating a beginning boundary and an ending boundary thatdefines the second measurement zone on the test strip.
 7. The method ofclaim 6, further comprising: a. depositing a sample on a test strip atan application region, the test strip including a third detection zonewith a third measurement zone; b. detecting a third detection signalarising from the third detection zone; and c. generating the baselinefor the third detection zone by interpolating between values of thethird detection signal outside of the third measurement zone and insideof the third detection zone.
 8. The method of claim 7, wherein the thirdmeasurement zone comprises a concentration of compounds that affect anintensity of a signal arising from the test strip, the compounds beingformed after the sample is deposited on the test strip.
 9. The method ofclaim 7, further comprising locating a beginning boundary and an endingboundary that define the third measurement zone on the test strip. 10.The method of claim 4, including quantifying the first and seconddetection signal of the first and second detection zone with respect tothe baseline.
 11. The method of claim 10, including quantifying thethird detection signal of the third detection zone with respect to thebaseline.
 12. The method of claim 10, comprising additional steps ofcomparing the first detection signal quantified from the first detectionzone with the second detection signal quantified from the seconddetection zone.
 13. The method of claim 11, including evaluating thefirst detection signal quantified in the first measurement zone on acurve defined by the second and third detection signal quantified fromthe second and third measurement zones.
 14. The method of claim 11,wherein the first measurement zone is formed from the concentration ofcompounds in an analyte binding zone on the test strip, and the secondand third measurement zones are formed from the concentration ofcompounds in a control zone on the test strip.
 15. The method of claim7, wherein the detection signals arising from the detection zones is alight intensity.
 16. The method of claim 15, wherein detecting the lightintensity comprises measuring a light reflectivity of the test strip.17. The method of claim 15 including determining a ratio of the lightintensity of each measurement zone and the baseline.
 18. The method ofclaim 7, wherein generating the baseline for each detection zoneincludes interpolating between the beginning and ending boundary of eachmeasurement zone using a straight line function.
 19. The method of claim7, wherein a processor and memory resources is coupled to a first sensorto detect the detection signals in each detection zones, and wherein theprocessor and memory resources generates the baseline in eachmeasurement zone.
 20. The method of claim 19, wherein first sensor is anoptical sensor.
 21. The method of claim 19, further including initiatingtiming of the lateral flow assay upon detecting a sample deposited onthe test strip.
 22. The method of claim 21, wherein an automaticstarting trigger coupled to the processor and memory resources detectsthe sample deposited on the test strip.
 23. The method of claim 22,including the step of measuring a change using a physical property ofthe sample to initiate timing the lateral flow assay.
 24. The method ofclaim 22, wherein the physical property of the sample being measuredincludes an electric field arising from the test strip containing thesample.
 25. The method of claim 22, wherein the physical property of thesample being measured includes the surface tension of the sample on thetest strip.
 26. The method of claim 22, wherein the physical property ofthe sample being measured includes conductivity of the sample on thetest strip.
 27. The method of claim 22, wherein the sample is detectedby an optical sensor coupled to the automatic starting trigger.
 28. Themethod of claim 21, further comprising: a. providing a pair ofconducting leads in proximity to an area of the test strip where thesample is deposited; b. applying an electrical potential across the pairof conducting leads to create an electrical field there between; c.introducing a sample into the electrical field to affect a change in theelectrical field, the sample being spaced from the electrical leads; andd. initiating timing of the lateral flow assay upon detecting the changein the electrical field.
 29. The method of claim 21, wherein theprocessor and memory resources initiates a timer for analyzing thelateral flow assay once the automatic starting trigger detects thesample of the test strip.
 30. The method of claim 21, wherein: a housingcontains the processor and memory resources, the automatic startingtrigger, and the first sensor; and the optical sensor measuresreflectivity of the test strip.
 31. The method of claim 19, wherein theprocessor and memory resources stores an assay matrix for a plurality ofassays.
 32. The method of claim 31, wherein the assay matrix includes aplurality of parameters for performing the multiple lateral flow assays,including parameters for incubation time and temperature control of thelateral flow assay.
 33. The method of claim 32, wherein the assay matrixmay be reconfigured by inputting information into the processor andmemory resources.
 34. The method of claim 32, wherein: the test strip iscontained within a cartridge having sensory codes; the housing includesa second sensor for reading the sensory codes; and a second sensorinputs information from the sensory codes to select assays from theassay matrix.
 35. The method of claim 34, wherein the sensory codes arebar codes, and the second sensor is a bar code reader.
 36. The method ofclaim 19, further comprising heating the test strip inside a housingwith a heater element, the heater element being coupled to the processorand memory resources to control temperature and incubation time.
 37. Themethod of claim 7, including: implementing an assay matrix in aprocessor and memory resources, the assay matrix containing a pluralityof parameters for performing the lateral flow assay; inserting the teststrip into the processor and memory resources; and controlling thelateral flow assay with the parameters of the assay matrix.
 38. Themethod of claim 34, wherein the assay matrix is reconfigurable withinformation transferred from a remote computer system.
 39. A method forperforming a lateral flow assay, comprising the steps of: a. providing atest strip on a cartridge, the test strip including a first analytebinding agent coupled to a detection agent and a second analyte bindingagent; b. depositing a sample on an application region of the test stripwherein at least a portion of the sample binds to the first analytebinding agent coupled to the detection agent to form a first analytebinding agent complex, the first analyte binding agent complex moving bylateral flow to a first detection zone that includes a first measurementzone, at least a portion of the first analyte binding agent complexbinding to the second analyte binding agent in the first measurementzone to form a second complex; c. detecting a first signal intensity inthe first detection zone; d. generating a baseline of a signal intensityfrom the first detection zone; and e. quantifying a value of the firstsignal intensity representative of the second complex with respect tothe baseline.
 40. The method of claim 39, wherein the step of generatingthe baseline comprises determining a background reflectance of the teststrip.
 41. The method of claim 39, wherein the baseline for the firstmeasurement zone is defined by interpolating between a value of abeginning and an ending boundary outside of the first measurement zonebut inside the first detection zone.
 42. The method of claim 39, whereinthe step of detecting the first signal intensity in the first detectionzone includes detecting a light intensity of the first detection zone.43. A method for performing a lateral flow assay, comprising: a.providing a test strip on a cartridge, the test strip including a firstanalyte binding agent coupled to a detection agent and a second analytebinding agent; b. depositing a sample on an application region of thetest strip wherein at least a portion of the sample binds to the firstanalyte binding agent coupled to the detection agent to form a firstanalyte binding agent complex, the first analyte binding agent complexmoving by lateral flow past a first detection zone having a firstmeasurement zone and to a second detection zone that includes a secondmeasurement zone at least a portion of the first analyte binding agentcomplex binding to the second analyte binding agent in the secondmeasurement zone to form a second complex; c. detecting a second signalintensity in the second detection zone; d. generating a baseline of asignal intensity from the second detection zone; and e. quantifying avalue of the second signal intensity representative of the secondcomplex with respect to the baseline.
 44. The method of claim 43,wherein at least a portion of the first analyte binding agent complexbinds to the second analyte binding agent in the first measurement zoneto form a second complex.
 45. The method of claim 44, wherein thebaseline for the second measurement zone is defined by interpolatingbetween a value of a beginning and an ending boundary outside of thesecond measurement zone but inside the second detection zone.
 46. Themethod of claim 43, wherein the step of detecting the second signalintensity in the second detection zone includes detecting a lightintensity for the second detection zone.
 47. A method for performing alateral flow assay, comprising: a. providing a test strip on acartridge, the test strip including a first analyte binding agentcoupled to a detection agent and a second analyte binding agent; b.depositing a sample on an application region of the test strip whereinat least a portion of the sample binds to the first analyte bindingagent coupled to a detection agent to form a first analyte binding agentcomplex, the first analyte binding agent complex moving by lateral flowpast a first and second detection zone having a first and secondmeasurement zone respectively, and to a third detection zone thatincludes a third measurement zone, at least a portion of the firstanalyte binding agent complex binding to the second analyte bindingagent in the third measurement zone to form a second complex; c.detecting a third signal intensity in the third detection zone; d.generating a baseline of a signal intensity from the third detectionzone; and e. quantifying a value of the third signal intensityrepresentative of the second complex with respect to the baseline. 48.The method of claim 47, wherein at least a portion of the first analytebinding agent complex binds to the second analyte binding agent in thefirst measurement zone to form a second complex.
 49. The method of claim48, wherein at least a portion of the first analyte binding agentcomplex binds to the second analyte binding agent in the secondmeasurement zone to form a second complex.
 50. The method of claim 47,wherein the baseline for the third measurement zone is defined byinterpolating between a value of a beginning and an ending boundaryoutside of the third measurement zone but inside the third detectionzone.
 51. The method of claim 47, wherein the step of detecting thethird signal intensity in the third detection zone includes detecting alight intensity for the third detection zone.
 52. The method of claim47, wherein the step of quantifying a value of signal intensity in eachmeasurement zone with respect to the baseline includes evaluating aratio of the intensity of the respective detection signals over thebaseline for each detection zone.
 53. A method for performing a lateralflow assay, comprising the steps of: a. applying an electrical potentialacross a pair of spaced apart electrical leads to create an electricalfield; b. introducing a sample into the electrical field to induce achange in the electrical field, the sample being spaced from the spacedapart electrical leads; and c. initiating timing of the lateral flowassay upon detecting the change in the electrical field.
 54. The methodof claim 53, wherein the step of introducing the sample into theelectrical field includes depositing the sample on a test strip insufficient proximity to the electrical leads to affect the electricalfield.
 55. The method of claim 54, wherein the electrical leads form acapacitor having a dielectric layer, and wherein the dielectric layerchanges when the test strip receives the sample.
 56. The method of claim53, wherein the step of initiating the lateral flow assay includesinitiating a processor coupled to the electrical leads to control thelateral flow assay.
 57. The method of claim 54, wherein the spaced apartelectrical leads comprise a pair of co-planar plates aligned insufficient proximity to the test strip to detect a change in adielectric constant between the coplanar plates and the test strip upondepositing the sample on the test strip.
 58. The method of claim 53,including the step of completing the performance of the lateral flowassay after an incubation time initiated by introducing the sample intothe electric field.
 59. The method of claim 53, further comprising: a.providing a test strip on a cartridge, the test strip including a firstanalyte binding agent coupled to a detection agent and a second analytebinding agent, the test strip being in sufficient proximity to theelectrical leads to affect the electrical field; b. depositing a sampleon an application region of the test strip to induce the change in theelectric field, wherein at least a portion of the sample binds to thefirst analyte binding agent coupled to the detection agent to form afirst analyte binding agent complex, the first analyte binding agentcomplex moving by lateral flow to a first detection zone that includes afirst measurement zone, at least a portion of the first analyte bindingagent complex binding to the second analyte binding agent in the firstmeasurement zone to form a second complex; c. detecting a first signalintensity in the first detection zone; d. generating a baseline of asignal intensity from the first detection zone; and e. quantifying avalue of the first signal intensity representative of the second complexwith respect to the baseline.
 60. The method of claim 59, including thestep of completing the performance of the lateral flow assay after anincubation time initiated by introducing the sample into the electricfield to affect the change in the electric field.
 61. The method ofclaim 60, wherein the incubation time is provided by an assay matrixstored in a processor and memory resources coupled to the electricalleads to control the lateral flow assay.
 62. The method of claim 61,wherein the processor and memory resources initiates a timer foranalyzing the lateral flow assay upon receiving a signal detecting thechange in the electrical field from introducing the sample onto the teststrip.
 63. A method for performing a lateral flow assay, comprising: a.depositing a sample on a test strip of a cartridge at an applicationregion of the test strip, the test strip including a first detectionzone with a first measurement zone; b. inserting the cartridge in ahousing having a processor and memory resources for storing a pluralityof assay tables; c. selecting a first assay table from a plurality ofassay tables to perform the lateral flow assay on the test strip; d.detecting an intensity of a first detection signal arising from thefirst detection zone of the test strip that includes the firstmeasurement zone; and e. quantifying a value of signal intensity for thefirst detection signal using a parameter from the assay table selectedfrom the plurality of assay tables.
 64. The method of claim 63, whereinat least a portion of the sample binds to a first analyte binding agentcoupled to a detection agent to form a first analyte binding agentcomplex, the first analyte binding agent complex moving by lateral flowto the first detection zone, and wherein at least a portion of the firstanalyte binding agent complex binds to the second analyte binding agentin the first measurement zone to form a second complex.
 65. The methodof claim 63, wherein at least a portion of the sample binds to a firstanalyte binding agent coupled to a detection agent to form a firstanalyte binding agent complex, the first analyte binding agent complexmoving by lateral flow past the first detection zone and to a seconddetection zone that includes a second measurement zone, at least aportion of the first analyte binding agent complex binding to the secondanalyte binding agent in the second measurement zone to form a secondcomplex, and the method includes the step of selecting the assay tablefrom the plurality of assay tables to perform the assay on the teststrip; detecting an intensity of a second detection signal arising fromthe second detection zone of the test strip that includes the secondmeasurement zone; and quantifying a value of signal intensity for-thesecond detection signal using a parameter from the assay table selectedfrom the plurality of assay tables.
 66. The method of claim 65, whereinat least a portion of the first analyte binding agent complex binds tothe second analyte binding agent in the first measurement zone to form asecond complex.
 67. The method of claim 63, wherein at least a portionof the sample binds to a first analyte binding agent coupled to adetection agent to form a first analyte binding agent complex, the firstanalyte binding agent complex moving by lateral flow past the firstdetection zone and a second detection zone having a second measurementzone, and to a third detection zone that includes a third measurementzone, at least a portion of the first analyte binding agent complexbinding to the second analyte binding agent in the third measurementzone to form a second complex, and the method includes the step ofselecting the assay table from the plurality of assay tables to performthe assay on the test strip; detecting an intensity of a third detectionsignal arising from the third detection zone of the test strip thatincludes the third measurement zone; and quantifying a value of signalintensity for the third detection signal using a parameter from theassay table selected from the plurality of assay tables.
 68. The methodof claim 67, wherein at least a portion of the first analyte bindingagent complex binds to the second analyte binding agent in the firstmeasurement zone to form a second complex.
 69. The method of claim 67,wherein at least a portion of the first analyte binding agent complexbinds to the second analyte binding agent in the second measurement zoneto form a second complex.
 70. The method of claim 63, wherein theplurality of assay tables may be reconfigured by transferringinformation into the processor and memory resources through an inputdevice.
 71. The method of claim 63, wherein the plurality of assaytables may be reconfigured by transferring information into theprocessor and memory resources through an optical code on the cartridge.72. The method of claim 63, wherein the parameters included in the firstassay table include an assay time for how long the lateral flow assay isperformed.
 73. The method of claim 63, wherein the parameters includedin the first assay table for use with the step of quantifying the valueof signal intensity for the first measurement zone includes a methodselection parameter for receiving an input that selects a method forquantifying the value of the detection signal for an output.
 74. Themethod of claim 63, wherein the parameters included in the assay tableinclude an assay temperature parameter for heating the sample to apredetermined temperature.
 75. The method of claim 63, wherein theprocessor receives a signal from an autostart trigger to initiate thelateral flow assay.
 76. The method of claim 65, wherein the step ofquantifying a value of signal intensity for the first, second, and thirdmeasurement zones includes evaluating the intensity of the detectionsignal for the corresponding detection zone with respect to a baseline.77. The method of claim 76, wherein the baseline is generated from thesignal intensity for first, second, and third detection zones.
 78. Anapparatus for performing a lateral flow assay, comprising: a housinghaving a receptacle for retaining a test strip that receives a sample,said test strip including a first detection zone with a firstmeasurement zone comprising a concentration of compounds that affect anintensity of a signal arising from the test strip, the compounds beingformed after the sample is deposited on the test strip; a sensor fordetecting a first detection signal arising from the test strip; and aprocessor and memory resources that generates a baseline for the firstmeasurement zone by interpolating between values of the first detectionsignal outside of the first measurement zone and inside of the firstdetection zone.
 79. The apparatus of claim 78, wherein: the test stripincludes a second detection zone with a second measurement zone, thesecond measurement zone comprising a concentration of compounds thataffect an intensity of a signal arising from the test strip, thecompounds being formed after the sample is deposited on the test strip;the sensor detects a second detection signal arising from the teststrip; and the processor and memory resources generates the baseline forthe second measurement zone by interpolating between values of thesecond detection -signal outside of the second measurement zone andinside of the second detection zone.
 80. The apparatus of claim 79,wherein: the test strip includes a third detection zone with a thirdmeasurement zone, the third measurement zone comprising a concentrationof compounds that affect an intensity of a signal arising from the teststrip, the compounds being formed after the sample is deposited on thetest strip; the sensor detects a third detection signal arising from thetest strip; and the processor and memory resources generates thebaseline for the third measurement zone by interpolating between valuesof the detection signal outside of the third measurement zone and insideof the third detection zone.
 81. The apparatus of claim 80, wherein theprocessor and memory resources executes code for generating a baselinethat locates a beginning boundary and an ending boundary for eachmeasurement zone on the test strip.
 82. The apparatus of claim 80,wherein the processor and memory resources executes code for quantifyingthe detection signal in each measurement zone with respect to thebaseline.
 83. The apparatus of claim 80, wherein the processor andmemory resources executes code for analyzing the lateral flow assay byevaluating the first detection signal on a curve defined by the secondand third detection signals.
 84. The apparatus of claim 80, wherein thefirst measurement zone is an analyte binding zone that receives ananalyte from the sample, and the second and third measurement zones areeach a control zone formed from combining a control agent and a controlbinding agent on the test strip after the sample is deposited on thetest strip.
 85. The apparatus of claim 84, wherein the sensor is anoptical sensor for detecting a reflection from each of the first,second, and third detection zones, and wherein the baseline representsan average reflection of the test strip excluding the measurement zones.86. The apparatus of claim 85, wherein the optical sensors are coupledto the processor and memory resources via an analog-digital converter.87. The apparatus of claim 85, wherein the processor and memoryresources executes code for quantifying a first, second, and thirdreflection signal by determining a difference between the reflection ofeach measurement zone and the respective baseline.
 88. The apparatus ofclaim 87, wherein memory resources store a plurality of assay tablesaccessible to the processor, and the processor executes code forquantifying the detection signal of each measurement zone by selectingan assay table from the plurality of assay tables.
 89. The apparatus ofclaim 88, wherein the processor receives input to select the assay tablefrom the plurality of assay tables.
 90. The apparatus of claim 89,wherein each assay tables stores a plurality of parameters including anassay time parameter for controlling how long the lateral flow assayselected is performed.
 91. An apparatus for performing a lateral flowassay, comprising: a pair of spaced apart electrical leads containedwithin a receptacle of a housing, the electrical leads receiving anelectrical potential to create an electrical field; and a test stripcontained within the receptacle, the test strip being in sufficientproximity to the electrical leads to induce a change in the electricalfield upon receiving a sample.
 92. The apparatus of claim 91, whereinthe electrical leads form a capacitor having a dielectric layer, andwherein the dielectric layer changes when the test strip receives thesample.
 93. The apparatus of claim 92, wherein a processor and memoryresources for controlling the lateral flow assay is coupled to theelectrical leads and initiates timing the lateral flow assay when thetest strip receives the sample.
 94. The apparatus of claim 93, whereinthe electrical leads comprise a pair of co-planar plates aligned insufficient proximity to the test strip to detect a change in adielectric constant between the coplanar plates and the test strip whenthe test strip receives the sample.
 95. The apparatus of claim 94,wherein the processor and memory resources analyzes the lateral flowassay after an incubation time that is initiated by introducing thesample into the electric field.
 96. The apparatus of claim 95, wherein:the test strip includes a detection zone with a measurement zone,wherein the first measurement zone comprises a concentration ofcompounds that affect an intensity of a signal arising from the teststrip, the compounds being formed after the sample is deposited on thetest strip, the processor and memory resources executes code forgenerating a baseline for the first measurement zone, and forquantifying a value of signal intensity for the first detection zoneWith respect to the baseline; and a first sensor detects the intensityof the signal arising from the first detection zone.
 97. The apparatusof claim 96, wherein the incubation time is provided by an assay matrixstored in the processor and memory resources.